If you use Alternate Start and your character visits Helgen, they will see Alduin flying away after he laid waste to the town. I use the excellent Alternate Start – Live Another Life mod, and it will direct your character to seek info on what happened at Helgen. If you avoid the quest triggers above, your character will not be “Dragonborn” (though some NPCs may call you that) and they may never (never say never) see a dragon again, as long as they avoid the quest triggers mentioned above. Please note that option 2 leaves a burning Western watchtower with Irileth and some of the Whiterun Guards waiting for your character, but no dragon will show up unless your character meets up with Irileth.
If you complete the Bleak Falls Barrow quest, avoid the Dragon Rising quest by not meeting Irileth at Whiterun’s Western Watchtower. Do not complete the Bleak Falls Barrow quest or 2. Visiting Helgen, by itself, will not put your character on a one-way path to becoming the Dragonborn. There are relatively simple ways to avoid becoming “Dragonborn” without mods: Avoid the Main Quest triggers.
